About last night. The biggest names in Hollywood are either sleeping in or grabbing Advil right about now. Taylor Swift, Leonardo DiCaprio and more let loose following the Met Gala on Monday, May 2, making their way to the spectacle’s official afterparty at the Boom Boom Room atop the Standard Hotel in downtown Manhattan.

The lavish annual shindig, which went until the wee hours of the morning, included impressive dance-offs, unlikely BFF bonding and a music set list saturated with Beyoncé’s latest Lemonade tracks.

Here, Us Weekly has rounded up the craziest moments:

Dance-Offs Were in Full Swing

Paul Rudd got his groove on with Michael B. Jordan and couple Kate Mara and Jamie Bell, an onlooker tells Us. The Ant-Man star even received a round of applause when he pulled out his best robot dance moves.

Paul Rudd attends the afterparty at the Standard Hotel following Manus x Machina: Fashion In An Age Of Technology.Roy Rochlin/Getty Images

Lady Gaga obsession!Ashley Olsen made her way through the crowd to get a front row seat to the singer’s surprise performance. Lady Gaga belted out “Hold Tight” and “Burn This House Down” while playing an electric guitar. Ashley and Mary-Kate Olsen also sang, rapped and danced around three bottle service women, the onlooker says. They left the nightclub around 3:15 a.m.

Who needs a dance floor? Emma Watson and her boyfriend, Matt Janney, stayed out late — and let loose. The Harry Potter alum jumped up on the bar and moved “her shoulders side to side,” the onlooker tells Us. She waved her hands in the air and went barefoot, too.

Dirty ‘Formation’ Sing-Alongs

And they slayed, slayed, slayed! The eyewitness tells Us that Beyoncé’s music was played during the majority of the night. In fact, Watson was the first to rock out to “Formation” with Aziz Ansari.

Beyoncé Knowles attending an afterparty following the Manus x Machina: Fashion In An Age Of Technology 2016 Costume Institute Gala in New York City.INFphoto.com

Katy Perry also was a part of the beyhive. The “Roar” singer was spotted “swinging her hips, throwing her hands” and singing along to the hit, the eyewitness notes. She notably sang the lyric “When he f–k me good, I take his ass to Red Lobster” to her beau, Orlando Bloom, who bursted out laughing in response.

Who knew these two were pals? Swift and Tom Hiddleston arrived at the Boom Boom Room together around 12:30 a.m. Swift, this year’s Met Gala cochair, seemed like the perfect host, as she hugged other attendees. The onlooker tells Us that she, Hiddleston and Sienna Miller chatted on the dance floor.

Taylor Swift and Tom HiddlestonRoy Rochlin/Getty Images; Wenn.com

Hiddleston also came to the rescue. Around 1 a.m., the Avengers star helped Swift change into her black combat boots. “Tom had to stand up and bang on the bottom of the shoe to get it on,” the eyewitness says. “Tom got the shoe on Taylor’s foot and she laughed.” (Frenemies Swift and Perry appeared to not cross paths.)

Sarah Jessica Parker was also spotted giggling — with none other than Megyn Kelly. The actress, 51, and Fox News host, 45, joined by Andy Cohen and Zachary Quinto, appeared to be in a serious conversation before they burst into hysterics. New mom Ivanka Trump and her husband, Jared Kushner, watched them from across the bar. (Donald Trump is set to sit down with Kelly for another interview following their feud.)

Meanwhile, perennial party boy DiCaprio arrived at 11:45 p.m. and left before 1 a.m. with three male buddies. Several attendees came up to greet him as he stayed in the back of the dance floor.

Nina Dobrev was just as low-key. The Vampire Diaries alum and Miles Teller hung out on the roof with the actor’s girlfriend, Keleigh Sperry.

Lovebirds After Dark

Some couples, meanwhile, kept to themselves. Alex Rodriguez stayed close to his love Anne Wojcicki. Wojcicki, the ex-wife of billionaire and Google cofounder Sergey Brin, sat on his lap and danced while drinking champagne. Rodriguez’s ex-girlfriend Kate Hudson also attended the Met Gala. (Rodriguez’s other famous ex, Madonna, also walked the red carpet.)

Across from the Yankees player, Jason Statham and Rosie Huntington-Whiteley sat at a table who briefly spoke to Rudd during their 30-minute stay.